Do you need sunscreen in the winter months?

St. Louis (KSDK) - Several cloudy days in a row make you wonder if you'll ever see the sun again.

On this week's 8 Ways to Prevent Cancer segment, we find out whether we really need to wear sunscreen during these darker months.

"So the short answer is yes," said Dr. Lynn Cornelius, a dermatologist at Siteman Cancer Center and Washington University School of Medicine.

Here's why; even on cloudy days, 80 percent of the sun's ultraviolet rays can pass through the clouds. And while glass in car windows filter out some of the ultraviolet B rays, ultraviolet A rays can penetrate.

"Particularly the side windows which are less protective," said Dr. Cornelius, "and when we see patients, if you are pretty observant you will notice that most people have more photo damage on the left side of their face than they do on the right."

You need even more sun protection if you're going to be out in the snow. The white stuff reflects 80 percent of all UV radiation.

And if you're lucky enough to go somewhere sunny during the winter, don't forget a thick layer of sunscreen.

"We don't want intermittent sunburns because that is a risk factor for the development of melanoma," said Dr. Cornelius.